In general, as coated tools, throw-away tips which are detachably attached to the tip portion of an insert holder to be used for turning or planing a work material such as various kinds of steel and cast iron, drills or miniature drills used for drilling or the like of the work material, end mills used for facing, grooving, shoulder milling, and the like of the work material, solid hobs and pinion cutters used for gear cutting of the work material into tooth shapes, and the like are known.
In addition, various suggestions have hitherto been made for the purpose of improving the cutting performance of coated tools.
For example, as described in Japanese Patent No. 3781374, a coated tool is suggested in which a surface of a cutting tool body made of tungsten carbide (hereinafter, referred to as WC)-based cemented carbide, titanium carbonitride (hereinafter, referred to as TiCN)-based cermet, or the like is coated with one or more hard layers having a cubic structure composed of a metal component primarily containing Cr, Al, and Si and at least one element selected from C, N, O, and B such that the fracturing resistance and wear resistance are improved.
In addition, Japanese Unexamined Publication No. 2008-31517 describes a coated tool in which a surface of a cutting tool body is coated with a hard coating layer, and at least one layer of a hard film is represented by (MaLb)Xc (where, M represents at least one metal element selected from Cr, Al, Ti, Hf, V, Zr, Ta, Mo, W and Y, L represents at least one additive element selected from Mn, Cu, Ni, Co, B, Si, and S, X represents at least one non-metallic element selected from C, N and O, a represents an atomic ratio of M to the sum of M and L, b represents an atomic ratio of L to the sum of M and L, c represents an atomic ratio of X to the sum of M and L, and a, b, and c satisfy 0.85≤a≤0.99, 0.01≤b≤0.15, a+b=1, and 1.00<c≤1.20), respectively. As a result, crystal grain refinement and crystal stability are achieved by Cu, Si, and the like which are the components of the hard film, and thus high-temperature hardness is increased, wear resistance is improved, and oxidation resistance is improved.
Further, Japanese Unexamined Publication No. 2004-50381 discloses a coated tool in which a hard coating layer formed of a complex nitride of Cr and Al is formed by physical vapor deposition on a surface of a cutting tool body. In the coated tool, the hard coating layer has a component concentration distribution structure in which a highest Al content point and a lowest Al content point are alternately and present repeatedly at predetermined intervals in a layer thickness direction and an Al content continuously changes between the highest Al content point and the lowest Al content point, the highest Al content point satisfies a composition formula: (Cr1-xAlx)N (where X represents 0.40 to 0.60 in terms of atomic ratio), the lowest Al content point satisfies a composition formula: (Cr1-YAlY)N (where Y represents 0.05 to 0.30 in terms of atomic ratio), and the interval between the highest Al content point and the lowest Al content point adjacent to each other is 0.01 to 0.1 μm. As a result, the hard coating layer exhibits excellent chipping resistance under heavy cutting conditions.